Optical networks primarily transport information from a source to a destination. The production, organization and consumption of this information is presently done almost exclusively in the electronic domain. Furthermore, it can be desirable for information within an optical network to be relayed in an electronic format between various segments of the optical network. To provide communication between the optical components and the electronic components, the optical data stream is converted to an electronic data stream by a photodetector. An electronic relay along an optical network can function to determine the route necessary for the next segment of the optical network and/or to “groom” the data stream to enhance the fidelity of the overall data link. Then, the data stream is reconverted into an optical signal using an optical emitter and directed into the appropriate next segment of the optical network, possibly being broadcast to multiple destinations through multiple segments. When a data stream reaches its ultimate destination, the optical signal is converted to an electrical signal with a photodetector, and the electrical signal is passed through a network interface or network appliance to the system consuming or otherwise using the signal, such as a computer or video-display device, such as a television.
In the time period roughly from 1998 to 2002, there were orders-of-magnitude increases in the capacity of communications systems for carrying digital information between distant locations, i.e., “long-haul,” and to a certain extent, within metropolitan regions. This increase in capacity was enabled to a significant degree by advances in the design and production of optical components for managing multiple simultaneous streams of digital optical data through ultra-fine wavelength discrimination. In its various forms, this wavelength discrimination is referred to as “Wavelength Division Multiplexing” or “WDM.” An example of particular components that have contributed to the capacity increase is planar lightwave circuits. With planar lightwave circuits, the circuits can be printed as compact, two-dimensional optical circuits in contrast with optical fiber-based systems using three-dimensional assemblies of discrete components assembled to micron-level precisions. Planar lightwave circuits are analogous with respect to form, impact and scalability to integrated circuit technology where complex electronic circuits are printed onto planar substrates and replicated in large quantities. Similarly, the replication process for planar optical circuits can provide a reduced cost when significant quantities of identical circuits are produced.
With the utilization of planar optical circuits, optical fibers generally are used for the long-range data transmission while the planar optical circuits are used for compact configuration of optical devices. Suitable interfaces are typically patterned as part of the planar lightwave circuit to connect the optical fibers to the planar optical circuits to form the optical subsystem. The optical subsystem is connected to electrical components to form the electro-optical data handling system. Connection of the electrical components to a planar optical circuit involves different considerations from the connection of electrical components to an optical fiber.